Carburetor



July 26, 1938. s. F. HUNT ET AL 2,124,777

CARBURETOR Filed Dec. 11, 1935 5 Sheets-Sheet 4 INVENTORS scoff F. Hun? Elmer Olson BY .Elml 0. Wirfh July 26, 1938. s. F. HUNT El AL CARBURE TOR Filed Dec. 1-1, 1935 5 Sheets-Sheet 5 z a a n m M n INVENTORJ scofi I. Hun-r Elmer Olson Wirfh Emil 0. x Q fig Patented July 26, 1938 UNITED STATES PATENT OFFICE CARBUBETOR Scott F. Hunt, Elmer Olson, and Emil 0. Wirth, South Bend, Ind., assignors to Bendix Aviation Corporation, South Bend, Ind., 21. corporation'of Delaware Application December 11, 1933, Serial No. 701,740

5 Claims.

the choke valye is closed,-the throttle valve will be prevented from closing, so as to subject the main fuel discharge nozzle to the suction of the engine to facilitate starting and to cause the engine to idle at a speed above normal while it is cold. v

Another object is to provide a carburetor of simplified construction which may be manufactured at a decreased cost and which will be economical and eflicient in operation.

Further objects and advantages of the invention will be apparent from the following description. taken in connection with the appended drawings, in which:

Figure 1' is a side elevation of a carburetor embodying the invention;

Figure 2 is a plan view of the same;

Figure 3 is a section on line 3-3 of Figure 2;

Figure 4 is a section on line 44 of Figure 2, showing the details of construction of one bar-- rel of the carburetor;

Figure 5 is a section on line 55 of Figure 2;

Figure 6 is an elevation showing the mechanism forcracking the throttle when the choke valve is closed;

Figure 7 is an elevation showing the connection from the hand throttle to the throttle shaft;

Figure 8 is a diagrammatic view showing the fuel and air passages in the carburetor;

Figure 9 is a view partly in section showing an improved check valve;

Figure 10 is a vertical section showing a detail of the fuel idling passage; t

Figure 11 is a vertical section showing a modified form of primary venturi; and

Figures 12, 13 and 14 illustrate a modified form of fast idle mechanism in three positions.

The tcarburetor shown in the drawings for purposes of illustrating this invention is of the plain tube down draft type. It is expressly understood, however, that the invention may be applied to other types of carburetor.

In the drawings, Figure ,1 shows a carburetor body comprising an upper or air horn section 20, a middle section 22 and a lower or throttle body section 24, the upper and middle sections being preferably formed of an alloy or metal suitable for die-casting,v while the lower body section is preferably formed of cast iron, and

consists essentially of two plain tubes or barrels formed integral in parallel relation and having relatively thin walls. The usual throttle valves 26 controlling the flow of mixture through the mixing chamber 28 are mounted in the barrels 30 on a common shaft 32 which extends through both barrels and is journalled in the walls thereof substantially as shown in Figure 5.

The lower body section 24 is formed of cast iron or other material of low heat conductivity to retard the flowof heat from the intake manifold to the float chamber 34 and main discharge nozzles 70. It is separated from the middle body section 22 by a gasket 38 of material of low heat conductivity. The upper section 20. comprises the usual air horn 40 consisting of a single passage and having mounted therein an unbalanced choke valve 42 of the usual construction carried by a shaft 44 and having a stem 46. fixed therein to contact the walls of the carbureting passage and prevent the choke valve from rotating beyond the full open position.

The air passage formed by the upper section 20 divides into two channels in the middle section 22, which channels connect with the two barrels 30 leading to different groups of engine cylinders. Each channel has mounted therein an inner and an outer venturi 52 and 54 in the usual relation. The inner venturis are cast integral with'the outer venturis and the middle section 22, being connected thereto by means of fins or bosses 56.

A float chamber 34 is cast integral with the middle section 22 and houses-a float 58 which controls the inlet valve 60 admitting fuel through the fuel supply duct 62 to the float chamber 34.

The. normal fuel level in the carburetor is indi-.

cated by broken lines X-X in Figures 3, 4 and 8. The float chamber 34 is provided with a cover 64 which may be cast integral with the air horn section.

Referring now to Figure 4, a main fuel nozzle i0 is seated in an inclined bore formed in the middle body section 22 and terminates within the inner venturi 52. The lower end of the inclined bore is enlarged to form a fuel well 16 which is closed by a threaded plug 14, and communicates with float chamber 34 by means of a large port 18 and one or more smaller ports 19. Under normal operation fuel will be admitted to fuel nozzle 10 from float chamber 34 throughports i8 and 79, but when the carburetor gets hot, a portion of the fuel will vaporize and the bubbles thus formed will pass out of fuel well I6 through port 18, thus obstructing in place by a metering plug 80 threaded in fuel 7 well I6 and provided with a metering passage 82 connecting fuel nozzle I0 and fuel well I6.

An air bleed passage 92 communicating with the air horn 40 through port 88 formed in the top of boss 56, is formed by a flattened portion of fuel nozzle I0, and communicates with said nozzle by means of ports 86, to provide air bleeding of the fuel nozzle.

The idling system comprises a vertical idling passage 94 having a vertical tube 96 therein, closed at its upper end by a metering plug 88 which communicates with a horizontal bore I04 (see Figure 8) formed in the middle body section 22 and communicating with a downwardly extending idling passage I08 which extends through the middle and lower sections 22 and 24 to the idling ports I I4 and I I6 which communicate with the mixing chamber on opposite sides of the throttle valve 26. The idling passage I08 is air bled from the air horn 40 by means of air bleed plug IIO so that a mixture of air and fuel is drawn through passage I08. The discharge from port II 6 is controlled by needle valve II8 which rlray be adjusted by means of an adjusting screw Figure 10 illustrates a modified vertical idling passage in which a ball check valve I00 is positioned in duct 88 to prevent air from entering through plug H0 and passing through bore I04 and duct 84 to the main fuel nozzle I0. Said check valve I00 is so positioned that it seats by gravity and will be unseated by auction in bore I04 when the idling system is in operation, to permit fuel to flow through duct 88 to the idling discharge port II6.

An acceleration pump cylinder I22 is cast integral with the middle body section 22 and communicates with the float chamber 34 through a check valve I24. A hollow plunger I26 slidable in cylinder I22 and actuated by means of rod I28 is formed with a flexible washer I30 fixed at the end of said plunger I26, extending back over the body of the plunger and urged against the walls of said cylinder I22 by means of a snap washer I34. This construction is designed to prevent vapor look when the fuel in the carburetor has been raised to a high temperature, since it will allow the entrained vapor to pass between the flexible washer I30 and the walls of cylinder I22. A slot I32 is provided between cylinder I 22 and float chamber 34 to equalize pressure in the two chambers and to insure a constant fuel level in cylinder I 22 regardiess of. theposition of plunger I26.

The plunger I26 is free to move longitudinally on rod I28 and is yleldingly urged to the lower extremity thereof by spring I 36 so that when the pump is actuated rapidly rod I 28 will move downward in plunger I 26, compressing spring I36. This construction is desirable because the outlet from the acceleration pump is restricted by a small metering orifice I38 and excessive pressure would otherwise exist which would retard the opening of throttle valve 26 if some means for relieving the pressure were not provided. Spring I36 will urge plunger I26 downwardly in cylinder. I22 and keep the entrained fuel under pressure to prolong the discharge of acceleration fuel. Spring I36 is fixed to shaft I28 by means of a washer I39 which is held in place by a key I fitted into a groove in shaft I28. A small spring I45 placed around shaft I28 and on top of washer I38 operates to hold a small washer I41 in contact with the upper surface of cylinder I22 to prevent dirt from entering said cylinder.

The check valve I24 between the acceleration pump and the fioat chamber is preferably of the type disclosed in Figure 9 and comprises a shell I25 provided with a head I21 having a screwdriver slot I29 and a hole I3I drilled through the end. A ball I 33 rests by force of gravity upon a seat formed in head I 21, and is retained in place by shearing rim I35 and crimping or bending a section I3'I toward the axis of the valve substantially as shown, thus securing the ball in place.

A pressure-responsive valve I40 controls the fiow of fuel discharged by the acceleration pump and comprises a plug threaded in a bore I42 having a duct therein communicating with the outlet passage I46. The movable member I46 of the valve has an upwardly projecting stem I50 designed to be engaged-by plunger I26. A compression spring I52 urges valve member I48 upward with sufficient force to prevent the flow of fuel through the valve except when plunger I26 is forced downwardly due to opening of the throttle valve 26, whereupon fuel pressure is exerted on member I48 and when suflicient to compress spring I52 member I48 will be forced from its seat and a charge of fuel pump through duct I46 and tube I58 to the acceleration nozzle I 56, which is positioned to discharge into the inner venturi 52 at a point opposite the end of the main fuel discharge nozzle I0. Tube I58 rises to a point above the fuel level XX and terminates at or slightly below said fuel level. This construction prevents siphoning of fuel when the engine is not running even though the valve I40 is defective so as to permit fuel to pass it.

The construction of the acceleration pump is such that if the throttle is opened slowly, the movement of plunger I26 in cylinder I22 will be proportional to the movement of the throttle valve 26 and a continuous discharge produced. If, however, the throttle is opened rapidly considerable pressure will build up in cylinder I22, and since the outlet is restricted by a small metering orifice I38 considerable time will be required to empty cylinder I22 sufficiently to permit plunger I26 to reach the bottom. The pressure will cause plunger I 26 to ride upwardly on rod I28, compressing spring I36 and permitting rod I28 to be fully depressed so as not to retard the opening of throttle valve 26. The fuel pressure below plunger I26 will rise sufficiently to compress spring I52, opening valve I 40 and permitting a charge of fuel to be discharged through the acceleration nozzle I56. If the throttle is maintained in full open position plunger I26 will be moved downwardly on rod I28 by the force of spring I36 as soon as sufficient fuel has passed through valve I40 to lower the pressure. When plunger I 26 reaches the bottom of cylinder I22 it will engage vertical stem I50 and hold valve I40 open permitting a steady flow of fuel through duct I46 by the suction in venturi 52 through tube I58 until vertical stem I50 is released by the movement of the throttle valve toward closed position.

The discharge tube I58 of the acceleration pump is seated in a bore I62 which communicates with passage I46, and tube I58 is held in place by means of a hollow tapered plug I66 which is placed around it and driven into bore I62 after the discharge nozzle I56 of tube I58 has been inserted into venturi 02, thus clamping the tube securely in place.

In the modified form of inner venturl shown in Figure 11, the body section I00 is formed with a tapered bore I10, and at its upper end is provided with a recess to receive an annulus I10. fitting therein and held in place by spinning a flange I12 at the top of body section I00 down over it, clamping it securely in place. The main fuel discharge passage 10 communicates with an annular fuel passage I14 formed in the body section I08, which passage forms with the annulus I10 the main discharge nozzle.

Referring more particularly to Figures 6 and 'l, the throttle valve 20 and choke valve 42 are interconnected in such a manner that as the choke valve 42 is moved in the closing direction the throttle valve 20 is opened a small amount to facilitate starting.

A lever I00 is pivoted by means of a pin 200 to the upper body section 20 of the carburetor at a point between the choke and throttle valves.

One end of said lever is provided with a cam surface I04 and two stops I00 and I08 to engage an ear I90 projecting laterally from an arm I92 which is fixed to choke shaft 44. A spring I94 connects ear I90 with an ear I90 formed on lever I00.

The other endof lever I00 connects with the choke actuating rod 200 designed to be actuated from the operator's seat, and imparts movement in the clockwise direction to lever I00 as the operator moves the choke actuating mechanism in the closed? direction. Between this point of connection and the pin 200 lever I00 is provided with a pin 202 which operates in a slot 204 in one end of a link 200. The other end of link 200 is pivoted on throttle shaft 32. An adiustable stud 200 having a locking spring 2I0 is threaded through link 200 and engages a stop 2l2 formed on one arm 2I4 of a triple armed bell crank fixed to throttle shaft 02. Another arm 2I0 connects with the acceleration pump actuating rod 222, while the third arm 2" connects with the actuating rod 229 from the foot accelerator, which rod is yieldingly urged toward the throttle closed position by a tension spring 22I in the usual manner, as indicated diagram-' maticallyv in Figure 6. An arm 224 rotatably mounted on the other end of throttle shaft 32 has an actuating rod 225, connected to accelerator and, by means of arm 220 having an ear 220 bent thereon'flxed to said throttle shaft 02, transmits positive motion to throttle valve 20. a

The normal positions of the choke and throttle valves when the engine is not running are shown in Figure 1 and in dotted lines in-Flgure 6, the choke valve 42 being open and the throttle valve 20 is closed. In order to prepare the carburetor for starting, the button on the dash panel (not shown) thereby rotating lever I80 in the clockwise direction about pin 230, from the position shown in dotted lines toward the position shown in full lines in Figure 6. During this movement spring I94 will exert tension on arm I92 through ear I80 which will slide on cam surface I04 and carry with it choke valve 42. As lever I00 rotates to the position shown in full lines in Figure 6, stop I00 will engage ear I90 andpositively rotate it until choke valve 42 comes in contact with the walls of the main carbureting passage which will arrest further rotatlonof lever I00.

as lever I90 moves from the position shown in the hand operator pulls out the choke;

dotted lines in Figure 6, pin 202' will slide in slot 204, causing lever 200 to rotate in the counterclockwise direction, whereupon stud 200 engage stop 2I2 and rotate the throttle in a counterclockwise direction, thereby opening it slight- 1y, as shown. When the engine has started, the operator will push the choke control button part way in and permit the engine to run a short time to warm up before pushing the choke control button all the way in. The above described interconnecting mechanism will hold the throttle valve open an amount proportionalto the closing of the choke valve, and therefore provide a fast idle for warming up purposes.

The fast idle mechanism just described does not form a part of our invention, but is disclosed and claimed in the copending application of M. A. Trisler, Serial No. 756,031, filed December 5, 1934.

Figures 12, 13 and 14 illustrate a modified fast idle mechanism comprising an interconnection between the choke and throttle valves by means of a link 240 having a fork 242 at its upper end, and slotted at the lower end to permit vertical movement of said link.

Thefork 242 is slidable on the choke shaft 44 between a washer 244 and the body section 20 of the carburetor. Onearm of the fork is provided with an ear 250 which is designed to engage a pin 252 extending through and fixed in choke shaft 44. Shaft 44 is mounted eccentrically of the air horn, so that the choke valve 42 is unbalanced or pressure responsive.

The lower end of link 240 slidably engages the throttle shaft 82 between the body section 24 of the carburetor and a triple armed bell crank 250 fixed to throttle shaft 02. Crank 258 imparts movement to the throttle by means of arm I is fitted with a connection 202 from the acceleration pedal- (not shown). Link 240 is provided with three steps 204, 200 and 208 which engage an adjusting screw 210 carried on arm 212. An ear 214 is provided on arm 210 to contact link 240 providing a stop when the throttle is in full open position. An ear 218 on the lower end of link 240 is provided to engage the cam surface 280 of arm 212 under certain operating conditions as described hereinafter.

Figure 12 shows the position of the mechanism when the choke valve is open and the throttle valve is closed. To prime and start the engine, the operator pulls out the choke-button on the dash panel, rotating choke shaft Min the counterclockwise direction and carrying therewith pin 252 which will engage car 250 on link 240 and force said link to slide upward, until the adjusting screw 210 in arm 212 contacts step 200 which will arrest further movement of the choke mechanism until the throttle has been partially opened by rotating bell crank 208 in the clockwise direction. This movement of crank 258 moves adjusting screw 210 out of the way of steps 200 and 200 and permits the choke valve to close, thus lifting link 240 by means of ear 250 and pin 252. When the throttle control is released, adjusting screw 210 will contact step 208 and hold the throttle partly open to condition the carburetor for starting. This stage of 'the operation. is illustrated in Figure 13. when the engine hasstarted, the operator pushes the choke control part way in, rotating pin 252 in the clockwise direction, and permitting link 200 to drop by force of gravity. Adiusting screw 210 will then engage step permitting bell crank 250 to rotate in the counterclockwise direction and close the throttle valve part way to cause the engine to idle at a speed above normal. When the engine is thoroughly warmed up, the operator pushes the choke button all the way in, and link 240 drops to the position shown in Figure 12 producing a normal or slow idle with the choke fully open.

This construction renders it impossible to close the choke valve unless the throttle is partly opened first, so that proper throttle setting is insured for starting and warming up purposes.

It will be understood thatthe fast idle devices described herein may be used in connection with automatic choke mechanisms such, for example, as that disclosed in the application of S. F. Hunt, Serial No. 630,274, filed August 24, 1932, in which the position of the choke valve. is controlled by temperature and other factors. In such a construction, if the engine should fail to start after considerable cranking with the choke valve closed, the engine may become flooded and it will be impossible to start it. Figure 14 illustrates a choke valve controlled by a thermostatic spring 282, and a method by which a flooded condition of the engine may be relieved.

If the engine is flooded, the throttle valve is thrown wide open as indicated in Figure 14, and as hell crank 258 rotates in the clockwise direction, cam surface 280 will engage ear 2'58 which is fixed to link m and force it down, partially opening choke valve d2 as ear 250 engages pin 252 and rotates it in a clockwise direction against the force of spring 282. Since choke valve 32 is unbalanced, it will be forced further open by the unrestricted flow of air to the cylinders of the engine and the excess of fuel will therefore be driven out through the exhaust valves and the engine prepared for a new attempt to start it.

It is expressly understood that the scope of this invention is to be in no way restricted except by the terms of the appended claims.

We claim:

1. In a carburetor having a main carbureting passage with choke and throttle valves mounted therein on shafts journalled in the walls of said main carbureting passage, an 22.1fm fixed to the throttle shaft, and a fast idle mechanism interconnecting said choke and throttle valves and comprising a link having one end bifurcated and its other end slotted to permit vertical movement of said link, means for lifting said link as said choke valve is closed, and a series of steps formed in the side of said link to engage said arm to hold said throttle partly open.

2. A carburetor venturi comprising a member formed of cast metal and having a tapered bore, an annular fuel discharge chamber adjacent the smaller end of said bore,- and an annular stamping overlying the fuel discharge chamber and spaced therefrom to form therewith an annular fuel discharge orifice, a portion of said first mentioned member adjacent said smaller end, being deformed to secure the annular member thereto.

3. In a carburetor having a carbureting passage with choke and throttle valves therein, separate means for actuating the choke and throttle valves, and a fast idle mechanism comprising a link having slidable engagement with the respective actuating means, means operative when the choke valve is moved toward closed position for moving said link longitudinally of the carburetor, and a plurality of stops carried by the link to variably limit the closing movement of the throttle valve.

QQIH a carburetor having a carbureting passage, a choke valve and a throttle therein, shafts for said choke valve and throttle, and means including a member slidably related to said shafts and operative in accordance with the position of the choke valve to variably limit the closing movement of the throttle, operative upon opening movement of the throttle to open the choke valve, and operative when the throttle is fully closed to prevent closing of the choke valve.

5. A device as defined in claim 4, including temperature responsive means for influencing the operation of the choke valve.

SCO'I'I F. HUNT.

ELMER OLSON. EMIL O. WIRTH. 

